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A Resistivity Gradient Piezoelectric FGM Actuator

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Journal of Materials Science & Technology 2000年第4期16卷 383-386页

作者： S. U.Adikary and Zhongyan MENG (School of Materials Science and Engineering, shanghai University, shanghai 201800, China) Dengren JIN (School of Materials Science and Engineering, shanghai Jiaotong University, shanghai 200030, China) School of Materials Science and Engineering Shanghai University Shanghai 201800 China School of Materials Science and Engineering Shanghai Jiaotong University Shanghai 200030 China

A resistivity gradient actuator based on lead zirconate titanate ceramics was successfully developed and the bending deflections up to 140 μm were obtained. The actuator material was a matrix of PZT ceramic into which smooth gradient of piezoelectric activity was introduced. The application of an electric field then causes the actuator to bend due to differential strains induced by the piezoelectric effect. The resistivity gradient of the actuator was achieved by doping PZT with suitable donor and acceptor dopants. PZT powder was modified and synthesized by using two stage powder fabrication method. The actuator was fabricated by uniaxial pressing followedby isostatic pressing with two layers of different resistivities.

关键词： PZT FGM

Robust On-Line Fault Diagnosis for Nonlinear Difference-Algebraic Systems Using Least Squares Estimate

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Journal of Systems Engineering and Electronics 2002年第2期13卷 50-59页

作者： Chen Yudong, Weng Zhengxin & Shi SongjiaoInstitute of Automation, shanghai Jiaotong University, shanghai 200030, P.R. China(Received April 9,2001) Institute of Automation Shanghai jiaotong University Shanghai 200030 P. R. China

A robust on-line fault diagnosis methor based on least squares estimate for nonlinear difference-algebraic systems (DAS) with uncertainties is proposed. Based on the known nominal model of the DAS, this method firstly constructs an auxiliary system consisting of a difference equation and an algebraic equation, then, based on the relationship between the state deviation and the faults in the difference equation and the relationship between the algebraic variable deviation and the faults in algebraic equation, it identifies the faults on-line through least squares estimate. This method can not only detect, isolate and identify faults for DAS, but also give the upper bound of the error of fault identification. The simulation results indicate that it can give satisfactory diagnostic results for both abrupt and incipient faults.

关键词： Difference equations Least squares approximations Robustness (control systems) Sensitivity analysis

NUMERICAL SIMULATION OF TIP-CLEARANCE FLOW IN CASCADE

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Journal of Hydrodynamics 2003年第1期15卷 62-66页

作者： Chen Long, Yang Chen jun, Wang Guo qiangSchool of Naval Architecture and Ocean Engineering, shanghai Jiaotong University, shanghai 200030, China School of Naval Architecture and Ocean Engineering Shanghai Jiaotong University Shanghai 200030 China

The tip-clearance flow in a cascade was numerically simulated by solving theRANS equations of incompressible fluids. The computational model was based upon the artificialcompressibility formulation proposed by Chorin. The Baldwin-Lomax turbulence model was used to makethe governing equations closed. For the specific structure of tip-clearance flow, a multi-block gridstructure was adopted to facilitate numerical compulations. The comparison of numerical resultswith experimental data indicates that the present method is capable of simulating tip-clearanceflows with satisfactory accuracy.

关键词： cascade flow tip-clearance flow multi-block grid structure

Continuous Separation of Inclusions from Aluminum Melt Flowing in a Circular Pipe using a High Frequency Magnetic Field

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Journal of Materials Science & Technology 2003年第3期19卷 221-225页

作者： Da SHU, Baode SUN, Ke LI, Jun WANG Yaohe ZHOUState Key Laboratory of Metal Matrix Composites, shanghai Jiao Tong University, shanghai 200030, China Lab. of Metal Matrix Composites Shanghai Jiaotong Univ. Shanghai 200030 China

The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magnetic field was investigated both theoretically and experimentally. The separation efficiency was calculated based on the trajectory method and compared with experimental results. It is found that the separation efficiency is a function ofnondimensional parameters ti . The effective way to improve the separation efficiency is to increase the effective magnetic flux density and decrease the pipe radius, and the value of should be kept about 2 in order to obtain the optimum separation efficiency.

关键词： Aluminum Inclusions Magnetic field Separation efficiency

Temperature Effects on the Self-trapping Energy of a Polaron in a GaAs Parabolic Quantum Dot

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Journal of Materials Science & Technology 1994年第2期10卷 131-134页

作者： Kadi ZHU and Shiwei GU (Institute of Condensed Matter Physics, shanghai Jiaotong University, shanghai, 200030, China)(To whom correspondence should be addressed) shanghai Jiaotong Univ Shanghai China

The temperature and the size dependences of the self-trapping energy of a polaron in a GaAs parabolic quantum dot are investigated by the second order Rayleigh-Schrodinger perturbation method using the framework of the effective mass approximation. The numerical results show that the self-trapping energies of polaron in GaAs parabolic quantum dots shrink with the enhancement of temperature and the size of the quantum dot. The results also indicate that the temperature effect becomes obvious in small quantum dots

关键词： GaAs Rev Temperature Effects on the Self-trapping Energy of a Polaron in a GaAs Parabolic Quantum Dot

Optimal motion planning of an underactuated spacecraft using wavelet approximate method

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Progress in Natural Science:Materials International 2006年第8期16卷 868-873页

作者： GE Xinsheng, CHEN Liqun and LIU Yanzhu (Beijing Institute of Machinery, Beijing 100085, China Department of Mechanics, shanghai University, shanghai 200072, China Department of Engineering Mechanics, shanghai Jiaotong University, shanghai 200030, China) [a]Beijing Institute of Machiner Beijing China [b]Department of Mechanics Shanghai University Shanghai China [c]Department of Engineering Mechanics Shanghai Jiaotong University Shanghai China

An optimal motion planning scheme using wavelet approximation is proposed for an underactuated spacecraft. The motion planning of an underactuated spacecraft can be formulated as an optimal control of a drift-free system. A cost functional is used to incorporate the control energy and the final state errors. The motion planning is to determine control inputs to minimize the cost functional. Using the method of wavelet, one can transform an infinite-dimensional optimal control problem to a finite-dimensional one and use Gauss-Newton algorithm to solve it for a feasible trajectory which satisfies nonholonomic constraints. The proposed scheme has been applied to a rigid spacecraft with two momentum wheels. The numerical simulation results indicate that optimal control with wavelet approximation is an effective approach to steering an underactuated spacecraft system from the initial configuration to the final configuration.

关键词： underactuated spacecraft motion planning optimal control nonholonomic constraint wavelet analysis.

MORPHOLOGY OF MELT SPINNING SUPERSATURATED B2 NiAl

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Acta Metallurgica Sinica(English Letters) 1996年第2期9卷 89-93页

作者： SUN Baode CHE Xiaozhou LIN Dongliang ZHOU Yaohe(Department of Materials Engineering,shanghai Jiaotong University,shanghai 20030,China)(Department of Materials Science,shanghai Jiaotong University,shanghai 200030,China) shanghai Jiaotong Univ Shanghai China

The morphology and structure of melt spinning Ni-33.6at% Al doped with B and RE were *** results show that the alloy consists of L10 martensitic grains and L12 Ni3Al at the grain boundaries when it contains no B and *** addition of 0.11-0.31wt% B can suppress the martensitic transformation and Ni3Al separation at the boundaries,and a supersaturated B2 single phase NiAl is *** addition of 0.05wt% RE can eliminate Ni3Al precipitated at the boundaries and get complete martensite,but 0.2-0.8wt% RE addition can suppress the martensitic transformation, and supersaturated B2 single phase NiAl is *** formation mechanism of supersaturated B2 single phase NiAl has been analyzed.

关键词： NiAl supersaturate morphologl melt spinning

A LINEAR HYBRID MODEL OF MSE AND BEM FOR FLOATING STRUCTURES IN COASTAL ZONES

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Journal of Hydrodynamics 2006年第6期18卷 649-658页

作者： ZHANG Jun MIAO Guo-ping School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai 200030China The First Engineers Scientific Research Institute of the General Armaments Wuxi 214035 China

A linear hybrid model of Mild Slope Equation （MSE） and Boundary Element Method （BEM） is developed to study the wave propagation around floating structures in coastal zones. Both the wave refraction under the influence of topography and the wave diffraction by floating structures are considered. Hence, the model provides wave properties around the coastal floating structures of arbitrary shape but also the wave forces on and the hydrodynamic characteristics of the structures. Different approaches are compared to demonstrate the validity of the present hybrid model. Several numerical tests are carried out for the cases of pontoons under different circumstances. The results show that the influence of topography on the hydrodynamic characteristics of floating structures in coastal regions is important and must not be ignored in the most wave period range with practical interests.

关键词： hybrid model Mild Slope Equation (MSE),Boundary Element Method (BEM) marine floating structures,coastal regions wave propagation wave force

Annealing High Resistivity CdZnTe Wafers under Controlled Cd/Zn Partial Pressures

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Journal of Materials Science & Technology 2004年第6期20卷 703-706页

作者： Wanwan LI, Wenbin SANG, Bin ZHANG, Jiahua MIN and Fang YUSchool of Material Science and Engineering, Jiading Campus, shanghai University, shanghai 201800, ChinaInstitute of Composites Materials, shanghai Jiao Tong University, shanghai 200030, China Sch. of Mat. Sci. and Eng. Shanghai Univ. Shanghai 201800 China Inst. of Composites Mat. Shanghai Jiaotong Univ. Shanghai 200030 China

In order to improve the performances of CdZnTe 7-ray detector, it is key issue to get the crystal with high quality. Equilibrium partial pressures, pCd and pZn, over Cd1-xZnx melt were estimated based on thermodynamic relationship and then Cd0.9Zn0.1Te wafers were annealed under controlled Cd/Zn partial pressures provided by Cd1-xZnx alloy reservoir. The experimental results show that when CdZnTe wafers are annealed under the equilibrium partial pressures provided by Cd0.99Zn0.01 alloy reservoir for 5 days or more at 1073 K, the resistivity of the wafer can be raised by 6 times and IR transmittance raised by 10% or more, the size and density of Te precipitates are greatly reduced. Moreover, losing of Zn from the surface can be avoided, which Ieads to improvement of the Zn radial distribution. In addition, the relationship between the electrical performances of the wafers and different controlled pressures is also discussed.

关键词： CdZnTe annealing Partial pressures over Cd_1-xZn_x γ-ray detector